Safety device for contact fuzes



"Much 1953 SAFETY DEVICE FOR coumc'r FUZES ToR . AT ORNEY United States Patent SAFETY DEVICE FOR CONTACT FUZEQ Henry H. Porter, Washington, D. C., assignor to the United States of America as represented by the Secretary of the Navy Application December 15, 1943, Serial No. 514,401

3 Claims. (Cl. 1022-49) This invention relates to point contact fuzes for projectiles and more particularly to an improved safety device therefor.

An impact fuze of the point contact type employs a firing pin operable upon direct contact with an object or target to detonate the charge in a projectile. In this type of fuze, the firing pin is mounted axially in the nose of the projectile and extends forwardly therefrom a distance sufiicient to allow the firing pin to be driven into the detonator upon contact of the firing pin with the target. It is therefore obvious that means must be provided to retain the exposed firing pin in safe position until the projectile is fired from the gun.

One of the principal objects of the invention, therefore, is to provide a safety device for fuzes of the type described which is operable to prevent premature shifting of the firing pin to detonating position.

Another object of the invention is to provide a point contact fuze safety device which, when the projectile is fired, will remain in an unarmed position until the setback force diminishes.

A further object of the invention is to provide a point contact fuze safety device which will be moved to armed position by the action of centrifugal force.

A still further object of the invention is to provide a safety device of this character which is of simple construction and is highly eificient in operation.

Other objects and advantages will appear in the following specification, reference being had to the accompanying drawing in which:

Fig. 1 is a longitudinal sectional view of a point contact fuze showing the safety device in the unarmed or safe position;

Fig. 2 is an enlarged fragmentary view, partly in section, showing the safety device and firing pin in the armed position;

Fig. 3 is a transverse sectional view taken in the plane indicated by line 33 of Fig. 1; and

Fig. 4 is a transverse sectional view taken in the plane indicated by line 44 of Fig. 1.

Referring to the drawing, the numeral indicates generally the nose portion of a contact fuze. Formed axially of the nose portion is a bore 11 communicating with a chamber 12 also in the nose portion. The chamber narrows toward its outer or forward end where it terminates in a land cooperating with an inwardly projecting boss 13 to define an annular groove 14 designed to receive a finger assembly 15 which will be hereinafter described.

Mounted for sliding movement within the bore 11 is a firing pin 16 comprising a rod 17 pointed at its inner end 17a which is designed to engage a detonator 26, the outer end of the rod projecting forwardly from the nose for engagement with the surface of a target. Since the firing pin is of small diameter, the area of its circular forward end also is small. This is both a desirable and a useful feature, because air pressure ahead of the firing pin will serve to drive the latter inwardly when it is released, yet not with suflicient force to puncture the detonator 26.

2,826,146 Patented Mar. 11, 1958 ice Near the pointed inner end 17a of the firing pin and integral therewith is a cylindrical head 18 having on its innermost or rear surface an annular recess 19 surrounded by an annular rim or shoulder 19a.

The finger assembly 15 comprises a circumferential flange 20 having a plurality of inwardly tensioned fingers 21 extending rearwardly from the flange. The fingers 21 terminate at their rear ends in inwardly and obliquely directed lips 22 normally engaging the annular shoulder 19a of the firing pin. Such engagement maintains the firing pin against rearward displacement, while forward displacement of the pin is resisted'by the pressure of the fingers 21 against the sides of the head 18. It is an item of some importance to confine the finger assembly to a unitary structure. By making it of a single piece of spring metal, the manufacture is facilitated and the cost reduced. The need of an auxiliary holding means for the firing pin is avoided, since the finger elements serve both as holding and tensioning means for the shoulder 18.

The finger assembly is mounted in the annular groove 14 and surrounds the firing pin 16, the assembly being retained rigidly in place by a sleeve 23 conforming to the wall of the chamber 12. One end 23a of the sleeve abuts and holds the circumferential flange 20, while the other end 23b is engaged by the casing 24 of the detonator 26. The detonator is screwed into the projectile casing 25, driving the sleeve forwardly in the chamber 12 and jamming the flange 20 into its rigidly seated position. Thus, the detonator 26 becomes the means for both driving the finger assembly home and maintaining it in its seated position through the medium of the sleeve 23.

The operation of the invention will now be briefly described. Prior to the firing of a projectile employing the new safety device, the firing pin 16 is normally held in unarmed position against accidental puncturing of the detonator 26, by engagement of the lips 22 of the fingers 21 with the annular shoulder 19a of the firing pin. At the moment of firing, the setback action of the firing pin causes the shoulder 19a to lock the lips 22, thus preventing the finger elements 21 from releasing the firing pin under centrifugal force while the projectile is within the bore of the gun.

However, the firing pin is released from the finger elements shortly after the projectile leaves the muzzle, as by that time the setback force has diminished substantially and the maximum velocity and rate of spin are attained. As centrifugal force is exerted upon the fingers 21 and lips 22, they are displaced outwardly against the tension of the spring fingers 21. The oblique form of the lips 22 thereupon exercises a cam action with shoulder 19a upon the head 18, moving it and the firing pin forwardly until the lips clear the shoulder 19a.

The air pressure upon the exposed, circular face of the firing pin then moves the latter rearwardly to the armed position in Fig. 2, but due to the restricted area of the front face of the pin, the total air pressure thereon is not great enough to force the point 17a into the detonator 26. The reduction in the rate of spin of the projectile is accompanied by an inward recession of the free ends of the fingers 21, so that the latter return into engagement with the firing pin, but this time with the exterior face of the head 18. By frictional engagement the fingers 21 will then grip the head of the firing pin, thus stabilizing the firing pin against any possibility, even though remote, of riding away from its armed position in contact with the detonator casing 24.

What is claimed is:

1. A projectile impact fuze having a nose portion and a chamber, and an axial bore communicating with the chamber, a boss projecting rearwardly in the chamber to define an annular groove, a firing pin movable in the bore, and a finger assembly in the chamber, said assembly including a circumferential flange surroundingthe boss and rigidly mounted in said groove said flange having longitudinally extending fingers, the fingers terminating in obliquely inwardly directed lips for engaging-the firingpin, said firing pin comprising a rod having an outer end projecting externally-of the nose; portion and terminatingat its inner end in a point for engaging adetonatonthe. rod'having near its pointed end ahead with a shoulder: for engagement with saidlips for normally retaining said. firing pinagainst inward displacement, but releasable by centrifugal force upon spinof the projectilefuze,.aftersetback, to arm said fuze.

2. A projectile. fuze having. a. nose portion with a chamber defining a. land, and a. communicating thread. course, a firing pin extending into thechamber, a spring finger assembly in the. chamber. to. hold. the firing pin against premature actuation, said" assembly including a. flange, asleeve in the. chamber engaging the flange, anda detonator screwed into the thread course to confront the firing pin, said detonator bearing against the sleeve 2 4 to hold the flange against the land and thus lock the finger assembly in the chamber.

3. In a projectile having aznose chamber, a bored boss, and an impact-operated firing pin mounted in the boss, the combination with a head on the pin alined with the boss and having a rear shoulder, of an annular flange mounted on the boss and means co-acting with the boss for anchoring the flange in the chamber, a group of resilient fingers integral with the flange, and cam lips on the fingers engaging the-shoulder, whereby the fingers are held in frictional contact with the boss and" head.

References Cited inthe tile of this patent UNITED STATES PATENTS 2,130,720 Junghans Sept. 20, 1938 2,168,482 Junghans Aug. 8, 1939 FOREIGN PATENTS 28,306. Great Britain 1908 447,875 Great Britain May 27, 1936 

